Can cannabis combat cancer?

The medical marijuana industry is growing in the US as more states ease cannabis restrictions [AP]

Scientists around the world continue to seek natural alternatives to fight cancer that don't destroy healthy cells - like radiation and chemotherapy do - in an effort to save millions of victims afflicted with the disease.

As World Cancer Day is marked on Thursday, a myriad of alternative cancer treatments have been reported by researchers showing promising signs - including wasp venom and a variety of herbs - after being tested in laboratories.

One potential alternative that has been a central subject of debate in the scientific community for decades is the plant cannabis.

While medical marijuana use has grown in prominence in recent years for alleviating symptoms of disease, a burgeoning body of scientific reporting suggests cannabis may also possess powerful anti-cancer properties.

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The plant has a long history of treating many different types of illnesses since ancient times. But it wasn't until the 1940s when scientists managed to extract a group of chemicals - known as cannabinoids - that have become prominent in modern medical research, and prompted the development of the International Cannabinoid Research Society.

Last year, the National Cancer Institute (NCI) for the first time announced that: "Cannabis has been shown to kill cancer cells in the laboratory."

"Studies in mice and rats have shown that cannabinoids may inhibit tumour growth by causing cell death, blocking cell growth, and blocking the development of blood vessels needed by tumours to grow. Laboratory and animal studies have shown that cannabinoids may be able to kill cancer cells while protecting normal cells," the NCI stated.

The NCI told Al Jazeera that since 2010 it has funded at least 36 cannabis-related research projects, noting that it funds only proposals of the "highest scientific merit".

The National Institute of Drug Abuse, another US government agency, also announced in 2015 that cannabis may have the capacity to combat tumours, citing a recent test on animals by researchers in Britain.

Dr Wai Liu - a research fellow at St George's University of London, who led the research project - told Al Jazeera that clinical trials had begun testing two cannabinoids against brain cancer in human patients after promising mice-tests.

Liu said some compounds in cannabis can alter the "signalling pathways" in cancer that "resist cell-death instructions".

"What we have shown is that cannabinoids can restore normal functioning of these pathways. This means that cancer cells are now able to die," Liu said.

"Our latest findings have shown that cannabinoids can combine effectively with irradiation to treat brain cancer. We showed that using these two together significantly reduced the sizes of brain cancer seen in mice.

"This data is very new and so exciting that clinical trials have started in patients with brain cancer."

Liu also led a study in 2013 that found six cannabinoids were effective against leukemia cells.

"These agents are able to interfere with the development of cancerous cells, stopping them in their tracks and preventing them from growing. In some cases, by using specific dosage patterns, they can destroy cancer cells on their own," he said in a press release.

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"Used in combination with existing treatment, we could discover some highly effective strategies for tackling cancer. Significantly, these compounds are inexpensive to produce and making better use of their unique properties could result in much more cost-effective anti-cancer drugs in future."

But he told Al Jazeera that "it is still too early to say if cannabinoids will work in humans".

Dennis Hill, a biochemist who had worked as cancer researcher for 10 years at the University of Texas MD Cancer Center – one of the country's leading cancer hospitals, told Al Jazeera how he avoided conventional treatments and cured himself of prostate cancer solely with cannabis oil.

In 2010, Hill was diagnosed with a late-stage aggressive adenocarcinoma and scheduled by his urologist to receive radiation therapy.

"I got to see patients pretty often and watched many people suffer and die from the treatments, so I knew I was not interested in that," he said.

In the meantime a friend of his recommended cannabis as a remedy and that prompted his research into it.

"As a biochemist, I understood the medical explanations that I read on how cannabis kills cancer cells," he said.

He then cancelled his appointment for the radiation treatment. After several months of consuming cannabis oil, the "cancer was completely gone", Hill said.

"It was amazing," he said, adding the side-effects were "very trivial".

However, Dr Otis Brawley, chief medical officer at the American Cancer Society, told Al Jazeera there was not enough scientific evidence to suggest cannabinoids were responsible for the remission and other factors could have played a role.

Hill said the plant needed to become legal for further research to thrive.

"As long as cannabis is on the federal government list of forbidden narcotics, it will not be available to researchers in this country. When cannabis is off this list, we will have plenty of research. Everyone is waiting, especially universities."

Dr Ralph Moss, who promotes both conventional and alternative cancer treatments, told Al Jazeera many obstacles have been put up against new treatments.

"The problem is that almost invariably scientific advances must also be highly profitable to clear the hurdles of the FDA [US Food and Drug Administration].

"This severely limits the number of drugs that can come to market, since unpatentable, out-of-patent, natural or generic medications are automatically ruled out by the demands of the marketplace. This issue, by the way, is almost entirely lacking from discussions of the pace of improvement in cancer treatment."